1. Technical Field
The invention relates generally to wood chippers. More particularly, the invention relates to a control system for controlling the feed wheel of a wood chipper wherein the feed wheel moves up and down to alter the size of a throat opening through which feed material is moved by the feed wheel. Specifically, the invention relates to such a control system having a throat sensor for determining the throat size and an electronic control unit for controlling rotation and down pressure of the feed wheel in accordance with the throat size.
2. Background Information
Typically, wood chippers include a feed chute, a rotating feed wheel and a cutting assembly whereby feed material is fed through the feed chute and drawn in by the feed wheel to the cutting assembly where the feed material such as branches and the like are cut by the cutting assembly. Some wood chippers utilize a single feed wheel while others utilize a pair of feed wheels which rotate in opposite directions to draw the feed material into the cutting assembly. Due to the various sizes of branches and logs that may be fed into a wood chipper, often the feed wheel or one of the feed wheels is movable in order to increase the size of the throat through which the feed material is drawn by the feed wheel. As disclosed in U.S. Patent Application Publication No. US2003/0111566 of Seaman et al., at least one wood chipper is known to have a feed control system which is hydraulically operated in order to provide additional pressure to the upper feed drum which corresponds to the pressure within the hydraulic motor which rotatingly drives the feed drum. Seaman et al. disclose a control system which when in automatic mode constantly urges the upper feed drum downwardly to apply a constant load to the feed material regardless of the position of the upper feed drum relative to the lower feed drum and thus regardless of the size of the gap between the two drums. The control mechanism of this wood chipper is entirely hydraulic in nature. More particularly, an increase in the load on the hydraulic motor which controls the upper feed drum causes an increase in the pressure of hydraulic fluid associated with the motor and this increased pressure of hydraulic fluid is directly applied to a hydraulic actuator to increase the down pressure on the feed drum. While this system has its advantages, it has also limited by the fact that the increased load on the feed wheel motor and thus the increased pressure on the hydraulic fluid can only be responded to by the increased down pressure of the feed drum. This control system is also operable in a manual mode in order to move the upper feed drum away from the lower feed drum to increase the gap to accommodate larger feed material or to provide additional down pressure on the feed drum when desired. Thus, while Seaman et al. provides certain advantages, there is still room for an improved feed mechanism for wood chippers.